I just viewed a video that showed a close-up of the deceased as he was receiving medical attention. Pretty sad to go out like that. Obviously, what else is there to expect when you go looking for trouble. It never ends well. These dumb kids.
I don't keep up with these events anymore so I'm not sure how they handle security. I suggest there be a parental supervision enforced. Minors can only get in with an adult. Secondly, teens (or pretty much anybody who looks suspicious) walking around in groups can and will be stopped by security to be questioned the whereabouts of their parent(s)/guardians. Their parent must be in close proximity.
We don't know the full story yet. Only bits and pieces. The rumor is that this was gang-related. One group was chasing rival members when the rivals turned around and fired shots. This is why it's important to close in on groups of teens wandering around. They apparently need adult supervision or else things can escalate quickly.